One of the principal components of currently known and manufactured bicycles is a component referred to as a "rear dropout". One of the primary functions of the rear dropout is to maintain and securely mount the axle of the rear wheel to the frame of the bicycle. In multiple speed (i.e. Gear) bicycles, the rear dropout further functions as a support structure wherein the rear derailleur of the bicycle is attached to a portion of the dropout referred to as the derailleur hanger. Currently, many types of rear dropout designs are known in the art. In this respect, the two most predominantly known design types are the "vertical" dropout and the "horizontal" or "slotted" dropout, both of which are named in reference to the direction the axle of the rear wheel is entered thereinto. With regard to vertical dropouts as currently known and manufactured, such dropouts generally have three major deficiencies associated with their designs.
The first deficiency relates to wheel alignment. A major function and advantage of using a vertical dropout, as opposed to a horizontal dropout, is the "self-centering" of the wheel within the frame of the bicycle achieved through the limitation of the rear axle movement in either a horizontal or vertical plane. However, as can be appreciated, any mis-alignment during factory installation of the dropout will cause the rear wheel to be out of its desired position with regard to the mechanical plane of the bicycle, thereby adversely affecting the bicycle's handling and braking characteristics. Currently known vertical dropouts contain no means for adjusting the axle of the rear wheel if such mis-alignment is to occur during manufacture or throughout the useful life of the bicycle.
The second deficiency relates to situations wherein the dropout is damaged. As previously specified, in multi-speed bicycles, one of the major components attached to the dropout is the rear derailleur which is used to selectively move the chain of the bicycle to various positions on the rear sprocket cluster. In certain instances, the derailleur is inadvertently entangled with some object while the bicycle is in motion, or is caught in the spokes of the moving rear wheel. When such occurs, invariably some damage will occur to the derailleur itself, the dropout, or both. In the worst case, the result is a broken and useless derailleur combined with a twisted and broken dropout, thus leaving the bicycle rider or user stranded and unable to easily repair the damage. The majority of presently known vertical dropouts are not configured so as to be easily removed and replaced when such damage occurs. In this respect, such dropouts are typically welded or soldered into the bicycle frame, thereby necessitating that the weld be broken to remove the damaged dropout and a replacement dropout be re-welded into place. As can be appreciated, such an operation must usually be conducted at a commercial repair establishment and generally involves a high cost.
The third deficiency associated with currently known vertical dropouts relates to derailleur positioning. Presently, there are no set standards for dropout dimensions with regard to the position of the derailleur hanger portion. With the advent of indexable shifting, it is imperative that when a derailleur and/or dropout is replaced, that the derailleur be positioned with respect to the axle of the rear wheel exactly as per the derailleur manufacturer's specifications. However, because no set dimensional standards exist, no currently known vertical dropout can position the multitude of differing available derailleurs in their required and/or optimum location.
Though a number of replaceable rear dropouts are known in the art, these dropouts are configured such that a relatively large portion of the dropout must be replaced if damaged, including the section which holds the rear wheel axle. In this regard, the large size and weight of the replaceable portion of these dropouts makes it unlikely that a rider will carry a spare replaceable portion. Additionally, the design of most of the presently known rear dropouts is such that a portion of the right seat stay (the portion of the frame that runs between the rear dropout and the upper portion of the frame near the seat) must be filed away or crimped to allow clearance for the bicycle chain when it is on the smallest freewheel cog of the sprocket cluster. This alteration of the seat stay has the disadvantage of creating a potentially weak point in the frame.
Thus, there exists a need in the art for a replaceable vertical dropout which alleviates the aforementioned three major problem areas associated with currently available vertical dropouts as well as the problems associated with currently available replaceable dropouts.